Suppress German silver (3)
I believe the answer is:
gag
'suppress' is the definition.
(thesaurus)
'german silver' is the wordplay.
'german' becomes 'g' (abbreviation**).
'silver' becomes 'ag' (Ag is the chemical symbol for silver).
'g'+'ag'='GAG'
(Other definitions for gag that I've seen before include "Prevent from speaking freely" , "Joke (colloq.)" , "Prevent free expression" , "Muzzle in palindrome form" , "Censor" .)